1. Field of the Invention
The invention relates to a wheel assembly, more particularly to a wheel assembly for a skateboard.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional skateboard 7 includes a footboard 8 and a wheel assembly 9 fixed on a bottom side of the footboard 8. The wheel assembly 9 includes a positioning seat 91, a wheel set 92 mounted below the positioning seat 91, and an adjustment seat 93 mounted pivotally on the positioning seat 91 through a shaft 94 and disposed below the footboard 8. When the center of gravity of a skater changes from left to right or right to left during use of the skateboard 7, the positioning seat 91 and the wheel set 92 rotate about the shaft 94 relative to the adjustment seat 93 so as to turn the footboard 8. Then, through coordination of a screw rod 96, an L-shaped plate 97, a packing ring 98, and a coil spring 99, which are all mounted in a receiving space 95 of the adjustment seat 93, with a circular rod 90 that is fixed on the positioning seat 91 and that extends through an opening 951 in the adjustment seat 93, the foot board 8 is restored to its original state.
However, during mounting of the screw rod 96, the L-shaped plate 97, the packing ring 98, and the coil spring 99 in the receiving space 95 of the adjustment seat 93, it is necessary that the coil spring 99 and the packing ring 98 be placed first in the receiving space 95. Then, the L-shaped plate 97 is placed in the receiving space 95 so as to cover the coil spring 99 and the packing ring 98 and to cause the circular rod 90 to extend through a hole 971 in the L-shaped plate 97. Afterwards, the screw rod 96 is passed through a hole 931 in the adjustment seat 93, through another hole 972 in the L-shaped plate 97, and through the coil spring 99 so as to engage threadedly a screw end 961 of the screw rod 96 with a screw hole 981 in the packing ring 98. Assembly, as such, is difficult since the screw rod 96 has to be threaded through the holes 931 and 972 and inserted into the coil spring 99 after the coil spring 99 and the packing ring 98 are covered by the L-shaped plate 97. Moreover, the coil spring 99 is different from an ordinary spring because the coil spring 99 must be stiff enough to provide a high restoring force such that the cost of producing the skateboard 7 is increased.